Trees was developed under a grant from the University of Pennsylvania School
of Arts and Sciences Instructional Computing Development Fund and is freely
available to Penn students and staff. Others who wish to use it must do so
under a license.

If you are not affiliated with an institution that has a site license for
Trees, you may download a demo of the Player for Trees for Windows [version
3.0.1]. The program will also run
in the WINE environment under Linux or Mac OSX. The download includes a grammar tool
useful in constructing trees for display in word processing documents and a MS Word file
of instructions on how to use the program. The download file is in zip format and must be
converted by "StuffIt Expander" or a similar program. If your Web browser is configured
to use the conversion program as a "helper" application, the conversion will happen
automatically.

The demo player version of the program will work with any grammar tool
written for Trees 3 but does not permit the writing of new grammar tools.
A sample of grammar tools that have been written at Penn for syntax courses is
available here.
The demo runs for 30 days after download. If you want to keep using Trees
Player after that time or if you want to write new grammar tools, you must
purchase the program. The cost for an individual user is:

$25 for the Trees Player

$50 for the full version with grammar tool writing

The full version of the program comes with a built-in
programming language Tree Talk, which allows users to write new grammar
tools with rules of syntactic composition that they specify. These grammar
tools are useful for creating homework exercises or exam problems in syntax
courses and for demonstrating how syntactic analyses work. There is an
accompanying manual that explains how to build these grammar tools.

Trees is available for purchase from the global internet reseller Kagi:

or from Google Wallet:

Multiple user site licenses are also available at higher cost for
instructors who want to use the program for teaching purposes. These
licenses include multiple copies of the full version of both the Windows and
the Macintosh flavors of the program. The program will also run under Linux, using the WINE
environment. For further information on the cost and
conditions of a site license, click here.